Love yourself.
People say it all the time, sometimes even without meaning, sometimes they have to tell other people as a way to make themselves believe it.
You could say: it's not as easy as it sounds.
I agree, trust me I 10000000000% agree.
But you can try. Even if you haven't been able to love, accept, or appreciate yourself for whatever reason, there is time, it is never too late. Now I am no personal trainer so I won't be there when you are walking to school, when you reading the newspaper on your way to work, or when you are sitting on the couch laughing at a scary movie because the characters are pretty dumb.
So my advice: BE YOUR OWN TRAINER! Put reminders on your phone- smile, be happy, you deserve to be happy, you're pretty, your hair looks cute today, I luv u, etc.
When you see them you will smile and they are small steps to loving yourself even if it doesn't feel like it or if it feels like it doesn't change anything, yeah it does.
If you are struggling with body image, block models on instagram, block fashion magazines, anything that will remind you of what "perfect" is. If you have a mirror in your room and you notice that whenever you look at it and you think something negative, either put a note with something positive on it or just get rid of the mirror (hide it because mirrors can be expensive and nobody had time to buy a new one).
I know that they are small things but the will slowly add up and the will make a change.
It took me a while to actually love myself, I'm still not quite there yet, if you ask I will give you a list about the things that I dislike about myself, but I will also give you an even longer list about the things that I love about myself.

Don't listen to people, if they have something negative to say, it most likely comes from a personal place of hurt. If you get called out for a bad hair day, they would have experienced it waaaay worse but they want to make you feel worse than they felt. I don't understand people.

I don't know you, I don't know your name, I don't know where you re from what you have done where you have been. But that's okay. I still love you.